E-300 for almost 2 years, just had auto focus problem - lens would not move when button depressed. Three calls to Olympus support could not resolve - said to mail them. I tried your suggestion and it solved the problem. When turning the lens, do not hold the button in (just enough to get rotation started) then put lens back on the body so it clicks.

When mounting the lens, you do not need to touch the button AT ALL. Just insert the lens and twist. The button should be pressed only when releasing the lens.